San Bernardino shooters practiced for attack a year in advance

NBC News has learned that San Bernardino shooters Syed Farook and Tashfeen Malik spent at least a year preparing for their terror attack, practicing at a local gun range and making financial plans for their family after their deaths.

Two sources said Farook and Malik had practiced their shooting skills at a Riverside, California area gun range for a year or more before last Wednesday's attack on a holiday office party. They killed 14 people and wounded 21 more with firearms at the Inland Regional Center in San Bernardino.

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San Bernardino shooters practiced for attack a year in advance

REDLANDS, CA - DECEMBER 4: Inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly the recent mass shootings, lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A Quran sits in the living room inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: An identification card for Syed Farook inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A hole in the ceiling could be seen inside the closet area of the rear bedroom inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A baby crib is seen inside the baby room of the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings, lived, on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A firearm lubricant could be seen in the closet of the front bedroom inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: Media reporters go in and out of the townhouse where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A praying mat and a cleared out closet in the baby room in the front of the apartment. A rare first glimpse inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly the recent mass shootings, lived, on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: Prayer beads are seen laying on the bed alongside personal documents in the rear bedroom inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A closet inside the baby room. A rare first glimpse inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings, lived, on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

REDLANDS, CA - DECEMBER 4: A rare first glimpse inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings, lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

A book sits on a table inside the home of San Bernardino mass murder suspect Syed Farook, December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

Journalists squeeze into a child's bedroom in the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

A view of the kitchen inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

A television crew prepares to do a live report inside a child's bedroom in the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

SAN BERNARDINO, CA - DECEMBER 04: Reporters take pictures of photographs found inside the home of shooting suspect Syed Farook on December 4, 2015 in San Bernardino, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: Baby food sits on a kitchen counter inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: A hatchet sits in a kitchen drawer inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: Reporters inspect the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: Arabic books sit in a closet inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: An Islamic Manners book sits in a bedroom inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: A book about prayer sits on a bedside table inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

SAN BERNARDINO, CA - DECEMBER 04: Reporters inspect the home of shooting suspect Syed Farook on December 4, 2015 in San Bernardino, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: Reporters inspect the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

REDLANDS, CA - DECEMBER 04: Reporters inspect the home of Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)

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Counterterrorism officials also told NBC News that Farook and Malik were making preparations for some time to "take care of both Grandma and the baby." The couple lived in a Redlands, California residence with their six-month-old daughter and Farook's 62-year-old mother, Rafia Farook. They left their daughter with Rafia on the morning of the attack,

Investigators are examining a $28,500 deposit made to Farook's bank account in the weeks before the Dec. 2 attack.

A U.S. counterterrorism official said that he didn't have details on the transfer, but that it "would be consistent with them making preparations for grandma and the kid."

See photos from the scene:

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San Bernardino active shooter, scene and police operations

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San Bernardino shooters practiced for attack a year in advance

REDLANDS, CA - DECEMBER 2: A SWAT team member stands watch with a rifle pointed at a home being investigated by police is shown after a mass shooting at the Inland Regional Center in San Bernardino December 2, 2105 in Redlands, California. Multiple fatalities and injuries were reported in the shooting (Photo by Marcus Yam/Los Angeles Times via Getty Images)

Law enforcement officers investigate a suspicious bag, later found not to be a threat, on Victoria Avenue after a mass shooting at the Inland Regional Center on Wednesday, December 2, 2015 in San Bernardino, California. At least 14 people were killed in a gun attack on a holiday party, triggering a massive manhunt that ended when police shot dead two heavily armed suspects -- a man and a woman -- on a quiet residential street. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)

SAN BERNARDINO, USA - DECEMBER 02: Yellow stripe is seen as the US Security Forces secure the area following a shooting that killed multiple people at a social services center for the disabled in San Bernardino, California of United States on December 02, 2015. Two suspects in a deadly mass shooting that killed 14 victims at a social services facility in California were killed after a confrontation with police, authorities said Wednesday. The initial shooting occurred earlier Wednesday when at least one shooter opened fire in San Bernardino at the Inland Regional Center, which provides services to persons with developmental disabilities and their families. At least 17 others were injured. (Photo by Mintaha Neslihan Eroglu/Anadolu Agency/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: A police officer officer guards a police line as officers prepare to raid the home of one or more suspects of a mass shooting at the Inland Regional Center by multiple gunmen on December 2, 2015 near San Bernardino, California. Police continue to investigate the shooting that left at least 14 people dead and another 17 injured. (Photo by David McNew/Getty Images)

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SAN BERNARDINO, CA - DECEMBER 2: Police place a marker along E. San Bernardino Ave. where a shootout occurred December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Rick Loomis/Los Angeles Times via Getty Images)

Armed police personnel walk along closed off streets in the San Bernardino neighborhood near the intersection of Richardson and Gould where a house was searched on December 2, 2015. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled in California were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: A police helicopter circles as officers search for a possible suspect following a shootout with suspects of a mass shooting at the Inland Regional Center by multiple gunmen on December 2, 2015 in San Bernardino, California. Police continue to investigate the shooting that left at least 14 people dead and another 17 injured. (Photo by David McNew/Getty Images)

Law enforcement officers search for the suspects of a mass shooting December 2, 2015 in San Bernardino, California. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)

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Law enforcement officers search for the suspects of a mass shooting December 2, 2015 in San Bernardino, California. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: A SWAT unit mobilizes near Richardson Street after a mass shooting at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at-large. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Law enforcement officers search for a possible suspect following a shootout with suspects of a mass shooting at the Inland Regional Center by multiple gunmen on December 2, 2015 in San Bernardino, California. Numerous deaths and injuries have been reported. (Photo by David McNew/Getty Images)

Law enforcement officers search for the suspects of a mass shooting December 2, 2015 in San Bernardino, California. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)

SAN BERNARDINA, CA - DECEMBER 2: A search team goes door-to-door looking for the third suspect in a residential neighborhood after a mass shooting at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at-large. (Photo by Marcus Yam/Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 02: A California Highway Patrol officer stands with his weapon as authorities pursued the suspects in a shooting that occurred at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Police continue to search for suspects in the shooting that left at least 14 people dead and another 17 injured. (Photo by Sean M. Haffey/Getty Images)

SAN BERNARDINO, CA - DECEMBER 02: A California Highway Patrol officer stands with his weapon as authorities pursued the suspects in a shooting that occurred at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Police continue to search for suspects in the shooting that left at least 14 people dead and another 17 injured. (Photo by Sean M. Haffey/Getty Images)

SAN BERNARDINO, CA - DECEMBER 02: A San Bernadino Sheriff helicopter flys above a neighborhood as authorities pursue suspects of the shooting at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Police continue to search for suspects in the shooting that left at least 14 people dead and another 17 injured. (Photo by Sean M. Haffey/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Officers swarm San bernardino Ave at Richardson Street near where suspects were shot in a black SUV December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Irfan Khan/Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Ambulances leave the scene of a mass shooting at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at-large. (Photo by Gina Ferazzi / Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Police draw guns on San Bernardino Avenue while chasing suspects in an SUV December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Francine Orr/Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Police draw guns on San Bernardino Avenue while chasing suspects in an SUV December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Francine Orr/Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Police and emergency vehicles line Waterman Avenue in front of the Inland Regional Center in San Bernardino, scene of a mass shooting on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Luis Sinco/Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Police and emergency vehicles line Waterman Avenue in front of the Inland Regional Center in San Bernardino, scene of a mass shooting on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Luis Sinco/Los Angeles Times via Getty Images)

Police at the scene of a shooting on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

SAN BERNARDINO, CA - DECEMBER 02: Members of the FBI Joint Terrorism Task Force stand outside of a press conference regarding the shooting that occurred at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by Sean M. Haffey/Getty Images)

SAN BERNARDINO, CA - DECEMBER 02: Ambulances pull out of a staging area near the Inland Regional Center where a shooting occurred earlier in the day on December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by Sean M. Haffey/Getty Images)

A heavily armed officer sets up a perimeter near the site of a shooting that took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: San Bernardino County Sheriffs deputies respond to a mass shooting at the Inland Regional Center December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by David McNew/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: A San Bernardino County Sheriffs Department investigator responds to a mass shooting at the Inland Regional Center December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by David McNew/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Employees and other people are evacuated by bus from the site of a mass shooting at the Inland Regional Center December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by David McNew/Getty Images)

Police escort civilians away from the 1300 block of S. Waterman Street near the site of a shooting took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

Police escort civilians away from the 1300 block of S. Waterman Street near the site of a shooting took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

Armed Sheriff's department personel man a roadblock at Waterman Street near the site of a shooting took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: Police and fire personnel secure the scene where a mass shooting occurred at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Gina Ferazzi / Los Angeles Times via Getty Images)

SAN BERNARDINO, CA - DECEMBER 2: San Bernardino police offices in SWAT gear secure the scene where a mass shooting occurred at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Gina Ferazzi / Los Angeles Times via Getty Images)

A crowd gathers behind police line near the scene of a shooting on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

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"They had purposely thought through that problem," said the official. "There were other indications of preparations."

Reuters reported that the loan to Farook was made by the on-line lender Prosper. In a statement, Prosper said that the company is "prohibited by law from disclosing any non-public, personally identifiable information regarding any loan originated through our platform."

"All loans originated through the Prosper platform are subject to all identity verification and screening procedures required by law, including U.S. anti-terrorism and anti-money laundering laws," the spokesperson said. "Like all Americans, Prosper is shocked and saddened by recent events in San Bernardino."